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Determinants

JEE Main 2024 (Online) 1st February Morning ShiftMCQMedium📈 Topic in 59% papers+4−1
Ques. 1JEE Main 2024, 1 February (Morning Shift)

If the system of equations 2x+3y-z=5 x+ y+3z=-4 3x-y+ z=7 has infinitely many solutions, then 13 is equal to :

  1. 1110
  2. 1120
  3. 1210
  4. 1220

Answer

(2) 1120

Solution

For infinitely many solutions the three planes must pass through one common line, so the first plane belongs to the family through the other two:

(2x + 3y - z - 5) = k1(x + y + 3z + 4) + k2(3x - y + z - 7)

Comparing coefficients: x: 2 = k1 + 3k2; constant: -5 = 4k1 - 7k2

These two give k2 = 1319, k1 = - 119

y: 3 = k1 - k2 57 = - - 13 = -70

z: -1 = 3k1 + k2 -19 = -3 + 13 = - 1613

13 = 13(-70) (- 1613 ) = 1120

Answer: (2)

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Ques. 2JEE Main 2024, 1 February (Evening Shift)

Let the system of equations x+2 y+3 z=5, 2 x+3 y+z=9, 4 x+3 y+ z= have infinite number of solutions. Then +2 is equal to :

  1. 22
  2. 17
  3. 15
  4. 28
Ques. 3JEE Main 2024, 31 January (Morning Shift)

If the system of linear equations x-2y+z=-4 2x+ y+3z=5 3x-y+ z=3 has infinitely many solutions, then 12 +13 is equal to

  1. 60
  2. 54
  3. 64
  4. 58
Ques. 4JEE Main 2024, 31 January (Morning Shift)

If f(x)= vmatrix x3 & 2x2+1 & 1+3x \ 3x2+2 & 2x & x3+6 \ x3-x & 4 & x2-2 vmatrix for all x R, then 2f(0)+f'(0) is equal to

  1. 24
  2. 18
  3. 42
  4. 48
Ques. 5JEE Main 2024, 31 January (Evening Shift)

Let A be a 3 3 real matrix such that A pmatrix1\\0\\1 pmatrix=2 pmatrix1\\0\\1 pmatrix, A pmatrix-1\\0\\1 pmatrix=4 pmatrix-1\\0\\1 pmatrix, A pmatrix0\\1\\0 pmatrix=2 pmatrix0\\1\\0 pmatrix. Then, the system (A-3I) pmatrixx\ \ pmatrix= pmatrix1\\2\\3 pmatrix has :

  1. exactly two solutions
  2. infinitely many solutions
  3. unique solution
  4. no solution
Ques. 6JEE Main 2024, 31 January (Evening Shift)

Let A be a 3 3 matrix and (A)=2. If n= ( 2024 times adj(adj( (adj A)))), then the remainder when n is divided by 9 is equal to .

Ques. 7JEE Main 2024, 30 January (Morning Shift)

If f(x)= vmatrix2 4x & 2 4x & 3+ 2 2x\ 3+2 4x & 2 4x & 2 2x\ 2 4x & 3+2 4x & 2 2x vmatrix, then 15f'(0) is equal to :

  1. 2
  2. 1
  3. 0
  4. 6
Ques. 8JEE Main 2024, 30 January (Morning Shift)

Consider the system of linear equations x+y+z=4 , x+2y+2 z=10 , x+3y+4 2z= 2+15 where , . Which one of the following statements is NOT correct ?

  1. The system has unique solution if 12 and 1, 15
  2. The system has infinite number of solutions if = 12 and =15
  3. The system is consistent if 12
  4. The system is inconsistent if = 12 and 1
Ques. 9JEE Main 2024, 30 January (Evening Shift)

Let R= pmatrixx&0&0\\0&y&0\\0&0&z pmatrix be a non-zero 3 3 matrix, where x =y ( + 2 3 )=z ( + 4 3 ) 0, (0,2 ). For a square matrix M, let trace (M) denote the sum of all the diagonal entries of M. Then, among the statements: (I) Trace (R)=0 (II) If trace (adj(adj(R)))=0, then R has exactly one non-zero entry.

  1. Only (I) is true
  2. Only (II) is true
  3. Both (I) and (II) are true
  4. Neither (I) nor (II) is true
Ques. 10JEE Main 2024, 30 January (Evening Shift)

Consider the system of linear equations x+y+z=5, x+2y+ 2 z=9, x+3y+ z= , where , R. Then, which of the following statements is NOT correct?

  1. System is consistent if 1 and =13
  2. System is inconsistent if =1 and 13
  3. System has unique solution if 1 and 13
  4. System has infinite number of solutions if =1 and =13
Ques. 11JEE Main 2024, 29 January (Morning Shift)

Let A= bmatrix1&0&0\\0& & \\0& & bmatrix and |2A|3=221 where , Z. Then a value of is

  1. 9
  2. 17
  3. 3
  4. 5

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